According to the current standards laboratory standards gnerally used in the US, someone who has a 12-hour fasting lgucose level between 65-109 is classified as normoglycemic. If the level is 110-125, they are classified as having impaired glucose tolerance. Above 125, they get a diagnosis of "frank" diabetes.

However, one can well imagine that blood glucose level is affected by a lot of factors--what one has last eaten, when, degree of physical activity recently done, what time of day the blood sample is taken (blood glucose tends to be lowest early in the day), etc. Moreover, the lab levels at which one is given these labels are fairly arbitrary (there's recently been a campaign to lower the "impaired glucose tolerance" category down to 100, for example), so many savvy endocrinologists are not comfortable using this test and these standards to diagnose diabetes/impaired tolerance. Most would rather at least get a set of Hemoglobin A1c levels over time--this measure of blood sugar tends to be more stable--and/or do glucose challenge through a several-hour glucose tolerance test. It's not rare for people with "normal" fasting blood glucose levels, and even "normal" hemoglobin A1c levels, to reveal an overreaction to glucose challenge during a multi-hour test that would lead an endocrinologist to suspect impaired tolerance or diabetes. (I know there were several people on the old Braintalk and at the Neuropathy Association boards who were diagnosed just that way.)

The better glucose challenges not only take a baseline blood sugar level before one drinks the measured glucose beverage, but a baseline insulin level, as well, and then they take blood and measure both glucose and insulin every half-hour for the duration of the test. Insulin and glucose levels interact--insulin drives glucose into the cells, and tends to rise and fall after it, in a time lag fashion--but in people who don't have good natural feedback mechanisms (this could be related to pregnancy, certain meds, or other health conditions in addition to glucose/insulin issues) there may be an overproduction of insulin to a given amount of glucose, driving the glucose levels down too low (reactive hypoglycemia), or an insufficent insulin response to a given amount of glucose, leading glucose levels to rise too much. The latter is impaired tolerance, and could signal developing diabetes. Indeed, even reactive hypoglycemia has an association with future possible impaired tolerance, as the insulin/glucose feedback mechanism has gone out of whack--the body is overproducing insulin, signalling insulin resistance in the cells, and if the body cannot at some point continue to compensate in that way, blood sugar may rise past healthy levels.

The levels that are accepted as being "normal" for blood glucose change during the course of the test. On my Quest results, you are allowed to be up to 159 at one hour, and up to 139 at two hours, and still be considered normoglycemic. At one hour, 160-225 signals impaired tolerance; at two hours it's 140-199. Above 225 at one hour or 199 at two hours signals diabetes. (The figures for pregnant women are slightly different.) As I said, there have been people who had normal fasting glucose levels who showed up with very high levels during the test and who were labelled with impaired tolerance or even diabetes.

I have the test done for at least three hours every year. The highest blood glucose level I ever received was 138 during the first hour. (My fasting glucose is generally in the 90-100 range.) But--my insulin levels tend to rise higher than the normal ranges during the test, and drive my glucose levels down into the 60's/70's during the second to third hour or so before the insulin recedes and my glucose normalizes. This is reactive hypoglycemia, and, along with the insulin levels, signals I have to be careful. It's why I try to keep muscle mass, which helps with insulin regulation, and why I take R-lipoic acid, and why I try to eat a sort of Zone like diet to keep too many wide swings in blood sugar from occurring.

Now, what does this have to do with Alan?

It's been speculated that most of us have some degree of insulin resistance impaired tolerance as we age, given our Western diet and lifestyles--and some of us from Northern/Western Europe may be more genetically prone to it than others. Of course, being overweight exacerbates this. I would think that given Alan's previous history (the weight, the heart issues), he probably had a degree of insulin resistance/impaired tolerance, at least at some point, and it may well have contributed to his symptoms. But, the two of you have made great lifestyle changes for him, and you may have dramatically reduced this, so that if this did contribute to his neuropathy, you may have arrested or even reversed the process. He may not show as impaired tolerant now, even if he once might have, and that's all to the good. (I'm trying to do a similar thing myself.)

Now, does this mean his symptoms AREN'T due to autoimmune issues, or to nerve pressure from the back? Not necessarily. He could be "co-morbid"--all, or any combination of these, could be involved. Neuropathy has many causes and mutliple things can damage nerves enough to produce symptoms. Often there's an "additive" phenomenon--diabetics are known, for example, to be more sensitive to nerve compression effects: a diabetic is more prone to develop compressive carpal tunnel than a non-diabetic, due to the fact that nerves in that area are already absorbing the blow that glucose dysregulation causes, so it's easier to produce symptoms from another casue than it would be in "normals". (I know my neuropathy has left me more prone to compressive effects, though, with its extremely acute onset, it's unlikely to have been caused originally be glucose problems--it's why I'm probably suffering now more form the cervical radiculopathy than someonw without "other issues" would.)

I'm certain Dr. Goldfarb will cover all the bases here, but it may be you never get any single "smoking gun" that explains Alan's neuropathy--he may have nerve assaults from a number of realms that add up to his symptoms.